Author Topic: Improved Refractometer Correction calculator  (Read 7196 times)

Offline Phil_M

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Re: Improved Refractometer Correction calculator
« Reply #210 on: March 12, 2018, 05:38:29 PM »
The last sentence of my "challenge" is worded as a question, not to be a smartie pants (well, maybe a little) but because it's entirely possible that I'm oblivious to why absolute accuracy is necessary.

I bottle with extract which is pretty much the only reason I care about accuracy. Unlike my keg Spunding brethren, I can’t bleed pressure once bottled.

I can’t see why anyone else would want to freak out.

This is back to the typical accuracy vs. precision argument. I certainly don't trust ANY of my homebrewing measuring devices to be accurate, save for perhaps my thermapen. But if they're precise, that won't matter. With multiple batches repeatable measurements will be all that was needed.

After all, mark on a stick units are how most measurements started, from temperature to density. We're getting so down in the weeds of this debate that we're losing sight of the purpose.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #211 on: March 12, 2018, 08:11:21 PM »
Yup. But that's cool. It's in our culture to bicker, but sometimes we should remember that we're all on the same side. Well, except people who dont like Fuggles!

Offline denny

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Re: Improved Refractometer Correction calculator
« Reply #212 on: March 12, 2018, 08:20:50 PM »
Yup. But that's cool. It's in our culture to bicker, but sometimes we should remember that we're all on the same side. Well, except people who dont like Fuggles!

I represent that remark!
Life begins at 60.....1.060, that is!

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Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #213 on: March 12, 2018, 08:22:59 PM »
On the flipside, what makes us think that density is a good measure of how the beer will taste?  It is well known that different sugars taste vastly different in a finished beer, so one 1.015 beer can taste sweet and another not at all.  Add alcohol into the density equation and you aren't even measuring one thing, but a balance - hence "apparent attenuation".  So, other than knowing when your beer is done, what is it really telling you?

I've been measuring with refractometer only for a while, and it tells me just as much about the final mouthfeel of a beer as density ever did.  It also helps to measure a variety of beer (commercial, other homebrews) and get an idea of what your target is for the style.  It's like going from F to C: you're never going to make the switch if you're constantly doing conversions in your head.  Think native!
Thank you. Pretty much what I was trying to say. I'm on my way to speaking °P. I switched all of my recipes to it. Kind of forces the deal.

Offline klickitat jim

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Re: Improved Refractometer Correction calculator
« Reply #214 on: March 12, 2018, 08:24:30 PM »
Yup. But that's cool. It's in our culture to bicker, but sometimes we should remember that we're all on the same side. Well, except people who dont like Fuggles!

I represent that remark!
Mister "dirt is cheaper"!

I'll double mash up Triple IPA with 100% brown malt and 100 IBUs of Fuggles, "Big Muddy"! Of course I'd need your feedback on every bottle
« Last Edit: March 12, 2018, 08:32:02 PM by klickitat jim »

Offline denny

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Re: Improved Refractometer Correction calculator
« Reply #215 on: March 12, 2018, 08:28:57 PM »
Yup. But that's cool. It's in our culture to bicker, but sometimes we should remember that we're all on the same side. Well, except people who dont like Fuggles!

I represent that remark!
Mister "dirt is cheaper"!

 ;D

Life begins at 60.....1.060, that is!

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Offline Petr

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Re: Improved Refractometer Correction calculator
« Reply #216 on: March 13, 2018, 01:35:03 PM »
Sorry, I didn't save my search results.  I just kept reading until I was assured there really is something going on here to confirm my suspicions.  I think all the non-alcohol factors, in the aggregate, can have enough impact that a formula based on one set of samples will not apply universally.  But if you are only interested in a certain margin of accuracy, I'm sure you can establish a correlation that works for you.  This really doesn't bother me, I just plan my brew length with a spare liter or so to allow for all the samples I might want to pull.  I realize this is not feasible for small batch brewers. I don't really have skin in this game. The amount of discrepancy between formulae,  each of which was empirically derived, just bothered me.  I wanted some insight.  Now everyone should just do what works for them!

Robert, you're wrong there. First of all, none of the formulae are based on one set of samples only. Non-alcohol factors (as hop compounds etc.) are significant for taste but because of their low concentration the effect on refractive index is negligible for our practical purposes and unless you'll provide me with an appropriate reference of otherwise I'll believe that I understand my professional field. You're chasing the wrong issue, as I said the real problem is that in some instances yeast is not necessary following precisely the same material balance glucose->ethanole + CO2 + biomass. Secondly, you're wrong that each of the formulas was just empirically derived. If you would take a look at that original reference that I provided you would see that there was a lot of insight into that formula and its form has a strong theoretical background. That is precisely the reason why my formula works for the whole fermentation and not just only for well-attenuated beer.

As you said everyone should use what works for them. I just provided another option for those who are interested. I have plenty of feedback that it works just fine for a lot, and there are fewer that has opposite experience and reasons for that are unclear to me even if I'm well aware of its limitations. I would love to find out reasons but that cannot do until I will really know details of each case with the actual data. My experience is that in the majority of cases it is due to misuse of the instrument or/and formulae or too high expectations about accuracy that just simply can't be better than 0.001-0.002 depending on particular circumstances.


Offline Petr

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Re: Improved Refractometer Correction calculator
« Reply #217 on: March 13, 2018, 01:51:29 PM »
On the flipside, what makes us think that density is a good measure of how the beer will taste?  It is well known that different sugars taste vastly different in a finished beer, so one 1.015 beer can taste sweet and another not at all.  Add alcohol into the density equation and you aren't even measuring one thing, but a balance - hence "apparent attenuation".  So, other than knowing when your beer is done, what is it really telling you?

I've been measuring with refractometer only for a while, and it tells me just as much about the final mouthfeel of a beer as density ever did.  It also helps to measure a variety of beer (commercial, other homebrews) and get an idea of what your target is for the style.  It's like going from F to C: you're never going to make the switch if you're constantly doing conversions in your head.  Think native!

No one claims that. FG is more of the process variable – it tells you how is the fermentation going, if it is done, how yeast performed, consistency between batches etc. with a deeper insight you can dig out even more. For instance, if yeast fermented maltotriose. It has also limited informational value about the body but that has to be considered in the whole picture of the taste. Yes, you're not measuring the variable directly and you're right that it measures the balance but the balance is relatively well understood with good accuracy for our purposes, so there is not much of the problem in that. The understanding allows us to measure things undirectly but reliably.


Offline dmtaylor

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Re: Improved Refractometer Correction calculator
« Reply #218 on: March 13, 2018, 01:57:37 PM »
Non-alcohol factors (as hop compounds etc.) are significant for taste but because of their low concentration the effect on refractive index is negligible for our practical purposes and unless you'll provide me with an appropriate reference of otherwise I'll believe that I understand my professional field. You're chasing the wrong issue...

Stronger wording eliminated, I agree with what was said right here above.  My sciency background brought me to the same conclusion: other chemical constituents besides water and ethanol are negligible and need not be considered here for refractometer measurements.  Their concentrations are just way way way too low to have any discernible effect on the margin of error.

Cheers.

David M. Taylor
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Michigan Tech
Class of 1997
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Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #219 on: March 13, 2018, 01:57:45 PM »
I certainly defer to you, Petr.  I got into this discussion because I was curious as to why this didn't seem to work for me:  or at least only occasionally worked.  I may have misinterpreted some of what I read, or the writers did.  It seems many of us get higher FG readings with hydrometer than any of the formulas predict.  As I said, I don't need a refractometer except pre-boil.  For those who do, I hope they find your formula serves their needs. It's astonishing how many times essentially this same conversation has been repeated on various forums.  It seems there is great interest in refractometers,  but a few intractable gremlins in the works! Carry on the good work.  BTW I appreciated your recent article on hop utilization, too.
Rob
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Offline Petr

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Re: Improved Refractometer Correction calculator
« Reply #220 on: March 13, 2018, 02:21:11 PM »
I certainly defer to you, Petr.  I got into this discussion because I was curious as to why this didn't seem to work for me:  or at least only occasionally worked.  I may have misinterpreted some of what I read, or the writers did.  It seems many of us get higher FG readings with hydrometer than any of the formulas predict.  As I said, I don't need a refractometer except pre-boil.  For those who do, I hope they find your formula serves their needs. It's astonishing how many times essentially this same conversation has been repeated on various forums.  It seems there is great interest in refractometers,  but a few intractable gremlins in the works! Carry on the good work.  BTW I appreciated your recent article on hop utilization, too.

Hear, hear. You know it depends on every one of us. I prefer the refractometer just because of the convenience of it – take few drops of wort and in a minute you have the reading, accurate enough for my purposes. In other cases as for low volume fermentation tests that I do for example for yeast hunting, it is even a necessity because I just can't afford the volume needed for the hydrometer. Glad you like the hop article!


Offline ynotbrusum

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Re: Improved Refractometer Correction calculator
« Reply #221 on: March 13, 2018, 06:16:02 PM »
I am grateful for you chemical engineering types for a deep discussion and interesting precision about gravity readings. 

I have no science background, though others in my family do.  I think I am just going back to my lab grade hydrometer (final gravity reading demarcation range only) and set up a small table of refractometer readings as compared to hydrometer readings for my typical low ABV beers over the next few batches.  That should get me in the ballpark, if I want to go with refractometer readings, alone.

I appreciate the deep water, but I think this is one area where I can't swim well enough and will have to watch from the knee deep level near shore.
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Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #222 on: April 24, 2018, 01:24:33 PM »
Don't want to get back into the weeds, just curious if anyone else who was having seriously questionable results with refractometer has seen improvement.  Tried it for kicks again last two batches.  During fermentation with actual saccharometer readings of 4.1°P and 4.5°P respectively, ALL the calculators gave results <0, so I didn't even bother when a batch finished out at 3.0°P.  Still use refractometer during mash, just still doesn't work for me in ferment.
Rob
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Offline Petr

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Re: Improved Refractometer Correction calculator
« Reply #223 on: April 24, 2018, 01:36:44 PM »
Don't want to get back into the weeds, just curious if anyone else who was having seriously questionable results with refractometer has seen improvement.  Tried it for kicks again last two batches.  During fermentation with actual saccharometer readings of 4.1°P and 4.5°P respectively, ALL the calculators gave results <0, so I didn't even bother when a batch finished out at 3.0°P.  Still use refractometer during mash, just still doesn't work for me in ferment.

I think that the answer for you if you're getting less then 0 as a result, is unfortunately simple. You're either using wrongly the calculators or your refractometer does not work as it is supposed to. What kind of refractometer do you have?

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #224 on: April 24, 2018, 01:43:18 PM »
An optical hand type, although I have a digital one on order (I really do find refractometers handy in the mash, and this should simplify my brewing.)  Again, don't really need it post boil, just curious.
Rob
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